Ultra-wide angle photographic lens

ABSTRACT

Ultra-wide angle photographic lens having a sufficiently long back focus suitable for use in a single lens reflex camera and consisting of six lens components of which the first to third lens components beginning at the object side are of negative power, the fourth, fifth and sixth lens components being of positive power, the second, third, fourth and sixth lens components consisting of cemented lens elements, while each of the first and fifth lens groups consists of a single lens element. The ultra-wide angle photographic lens satisfies the following conditions:

JDUQOU SR r T U United Stat; *A W66 [111 3,741,630

Nakagawa June 26, 1973 ULTRA-WIDE ANGLE PHOTOGRAPHIC second, third, fourth and sixth lens components com I LENS sisting of cemented lens elements, while each of the [75] Inventor: mm N'hgw" Tokyo, Japan first and fifth lens groups consists of a single lens element. The ultra-wide angle photographic lens satisfies [73] Assignee: Olympus Optical Co., Ltd., Tokyo, the following conditions:

Japan f f "2.5 f 221 Filed: Nov. 5, 1971 [21] Appl. No.: 196,080

(2) 52 US. Cl. 350/214, 350/176, 350/215 E51} 161. CI. G02b 9/62, G02b 9/62 [58] Field of Search 350/214, 215 (3) f r 3.5f [56] References Cited (4) UNITED STATES PATENTS 30 1/ 50 3,524,697 8/1970 lsshiki 350/215 ux (5) Primary Examiner-John K. Corbin gfi gocal length of the entire system Anomey Kurt Kelman f resultant focal length of the first to third lens 57 ABSTRACT components, inclusive I I Ultra-wide angle photographic lens having a suffigg raging of i ip g f ciently long back focus suitable for use in a single lens Z f f z" :fi e ens reflex camera and consisting of six lens components of d thickess 5 theglens and air a i which the first to third lens components beginning at t th g the object side are of negative power, the fourth, fifth egmmng a e o Jec we and sixth lens components being of positive power, the 4 Claims, 4 Drawing Figures PATENTED JUN 26 I975 3.141.630 said 2 org CHROMATIC SPHERICAL ABERRATION ASTIGMATISM ABERRATION DISTORTION OF MAGNIFICATION 47!! 4% 9O. Fgc

055673 05 0.77661 -100% 0* j JA r Q-JB rJC IJIIIIIYIYE u*-JD 1 ULTRA-WIDE ANGLE PHOTOGRAPHIC LENS BACKGROUND OF THE INVENTION The present invention relates to an ultra-wide angle photographic lens, and more particularly, to an ultrawide angle high quality photographic lens (to be referred to as a fish-eye lens hereinbelow) which is compact in size and has an angle of field of 180", a large aperture of F2,8 and a long back'focus (the distance between the back lens and the image) so that the lens can be mounted in a single lens reflex camera without requiring to swing up the reflecting mirror of the camera thereby permitting the object to be observed through the finder of the camera when the lens is mounted.

The present invention is directed to improvements in the fish-eye lens.

SUMMARY OF THE INVENTION that the object is observed through the view finder of the camera, and in which various aberrations are well compensated for.

The fish-eye lens of the present invention comprises a first lens component beginning at the object side consisting of a single negative meniscus with its convex surfaces directed to the object side, a second lens component consisting of two lens elements cemented to each other to form a negative meniscus as a whole with the convex surfaces thereof directed to the object, a third lens component consisting of two lens elements cemented to each other or closely spaced from each other by a small air gap so as to have a negative power as a whole, a fourth lens component consisting of two lens elements cemented to each other and having a positive power, a fifth lens component consisting of a single positive meniscus with its concave surfaces directed to the object side, and a sixth lens component consisting of two lens elements cemented to each other and having a positive power.

Since a fish-eye lens has normally a large negative distortion, the first to the third lens components are each made to have a heavy negative power in accordance with the present invention so as to make the back focus long while the aberrations can be well compensated for over the large angle of field of I80". Further, cemented surfaces are provided in the second lens component having a large height of light rays in the oblique light bundle therethrough so that the compensation for the chromatic aberration of magnification is made effective, and the third lens component is constituted by substantially a hyperchromatic lens or two lens elements closely spaced from each other by a small air gap instead of the provision of the cemented surfaces of the hyperchromatic lens and the fourth lens component located at a position where the light bundle diverges is constituted by two lens elements cemented to each other, so that the compensation for the axial aberration is made effective, while the sixth lens component is constituted by two lens elements cemented to each other and each having Abbe number largely different from each other so that various aberrations are well compensated for. Particularly, in accordance with the characteristic feature of the present invention described above, the chromatic aberration of magnification can be well compensated for which is the serious problem in the compensation for the aberrations in a wide angle lens.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectional view showing an embodiment of the fish-eye lens constructed in accordance with the present invention in which the third lens component is constituted by two lens elements cemented to each other;

FIGS. ZA-ZD are diagrams showing respectively the spherical aberration the astigmatism, the chromatic aberration of magnification and the distortion of the fisheye lens of FIG. 1;

FIGS. 3A-3D are diagrams similar to FIG. 2 but showing the aberrations of the second embodiment of the present invention in which the third lens component is constituted by two lens elements closely spaced from each other by a small air gap; and FIG. 4 is a longitudinal sectional view showing the second embodiment of the fish-eye lens wherein the third lens component is constituted by two lens elements closely spaced from each other by a small air gap.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the first embodiment of the fisheye lens of the preSent invention comprises six lens components of which the first lens component I beginning at the object side is a single negative meniscus with its convex surfaces directed to the object side, the second lens component II being two lens elements cemented to each other to form a negative meniscus as a whole with the convex surfaces thereof directed to the object side, the third lens component III being two lens elements cemented to each other to form a negative lens as a whole, the fourth lens component IV being two lens elements cemented to each other to form a positive lens as a whole, the fifth lens component V being a single positive meniscus with its concave surfaces directed to the object side, while the sixth lens component VI consists of two lens elements cemented to each other to form a positive lens as a whole.

The fish-eye lens of FIG. 1 satisfies the following conditions:

f the focal length of the entire system f,,, the resultant focal length of the first to third lens components, inclusive r (i l 16 the radius of curvature of each of the lens elements, i beginning at the object side d, (i l 15) the thickness of each of the lens elements and the air gap between the adjacent lens elements, i beginning at the object side n, (i l the refractive index of each of the lens elements, i beginning at the object side 11; (i l 10) Abbe number of each of the lens elements, 1' beginning at the object side As described previously, a fish-eye lens has usually a large negative distortion, and the first to the third lens components l to ill of the fisheye lens are each constituted by a lens component having a large negative power in accordance with the present invention, so that the back focus is made long while the compensation for the aberrations is made effective over the wide angle of field of 180. Further, cemented surfaces are provided in the second lens component I! so that the chromatic aberration of magnification is effectively compensated for. The third lens component III is constituted by a hyperchromatic lens while the fourth lens component IV is constituted by cemented lens elements, so that the axial aberration is effectively compensated for. The sixth sixth lens component V] is constituted by two lens elements cemented to each other and each having Abbe number greatly different from each other, thereby permitting various aberrations to be effectively compensated for.

Particularly, the chromatic aberration of magnification can be effectively compensated for in accordance with the present invention.

With regard to the condition (1) above, if the value f l is smaller than the value f, Petzval sum is made excessively large in the negative value, so that the aberration such as the curvature of field cannot be effectively compensated for, although the back focus can be made long. On the other hand, if the value lf l is made greater than the value 2.51, it is made difficult to make the back focus long while non-axial aberrations can not be effectively compensated for over the wide angle of field of 180.

Under the condition (1) above, it is desirable for effectively compensating for the aberrations that the cemented surfaces of the lens elements are made to have a positive power and that the convex side of the cemented surfaces is directed to the object side. To this end, the requirement n n; in the condition (2) is indispensable in the present invention. Further, if the value r, exceeds beyond the upper limit 35for the lower limit f in the condition (2), a large spherical aberration and a large astigmatism will result and the compensation therefor is made difficult, particularly, in case the value r is made smaller than 15f, undercorrection of the chromatic aberration will result thereby making it difficult to appropriately compensate for the chromatic aberration.

The above condition (3) relates to the condition (2) and the condition (3) is necessary for the compensation for the chromatic aberration of magnification. Thus, by satisfying the requirements v v ,f r, 3.5f in accordance with the condition (3), the chromatic aberration of magnification which has been compensated for by the condition (2) can be further corrected. On the other hand, if u v then the compensation for the axial chromatic aberration is made difficult and the chromatic aberration of magnification cannot be effectively compensated for. if the value r, is made smaller than the valuef, overcorrection of the chromatic aberration of magnification will result, while remarkable undercorrection of the chromatic aberration of magnification will result, if the value r, is made greater than 3.5 f. v

The condition (4), i.e., the limitation of the value r within the range off and 3.5f, is indispensable for the compensation for the spherical aberration, astigmatism and the coma. If the value r is made smaller than the value f, then these aberrations are made excessively large, whereas the reverse conditions are generated when the value r is made greater than the value 3.5 f, thereby making it difficult to appropriately eliminating these aberrations.

With regard to the condition (5), if the value 1 is made greater than 30 while the value v is made smaller than 50, undercorrection of axial chromatic aberrations and the chromatic aberration of magnification will take place so that the compensation for the aberration is made difficult. Therefore, the condition (5) is indispensable in the present invention.

Following table 1 shows an example according to the first embodiment of the present invention.

TABLE] 6. 1.589111, 61.0 r, 2.5106 d, 2.3830 r, 8.4135 11, 0.5167

- 6, 1.7847 v, 25.6 r, 1 8.4891 a. 0.2432

n, 1.5891 11, 61.0 r, 2.1550 :1, 1.7556 1 r, 379278 4. 0.1945

n. 1.67 v. 57.3 r 2.1550 d 0.5957 n l.6668 v, 33.0 r, 12.2238 a. 1.0057 r, 18.9741 d, 0.2432

n.' l.7865 v, 50.1 r l.3584 a 0.8377

8. 1.5173 v, 69.3 3.1809 d 0.0243 r 3.3374 11,. 0.1824

n 1.5173 11,, 69.3 r 3.640l

f f 23 Back focus f 4.5855

As is clear, the fish-eye lens has a sufficiently long back focus.

The spherical aberration, the astigmatism, the chromatic aberration of magnification and the distortion of the above embodiment are shown in FIG. 2. As shown in FIG. 2, it is apparent that the aberrations are well compensated for.

In accordance with another feature of the present invention, the third lens component may be modified so that it consists of two lens elements closely spaced from each other by a small air gap, noting FIG. 4. The third lens component of the second embodiment effects substantially the same function as that of the previously described first embodiment of the present invention.

in this case, the fish-eye lens of FIG. 4 must satisfy the following conditions:

where:

f= the focal length of the entire system f the resultant focal length of the first to third lens components, inclusive r, (i l 17) the radius of curvature of each of the lens elements, i beginning at the object side d, (i =1 16) the thickness of each of the lens elements and the air gap between the adjacent lens elements, i beginning at the object side in (i l 10) the refractive index of each of the lens elements, 1 beginning at the object side v,- (i 1 l) Abbe number of each of the lens elements, i beginning at the object side The reasons for setting the above conditions l) to in the second embodiment are similar to those for the first embodiment previously described so that the detailed description therefor is not necessary here.

Following table 2 shows an example in accordance with the second embodiment of the present invention.

TABLE 2 n, 1.5891 v, 61.0 r 2.3973 11, 2.0581 r 6.7504 d 0.4841 n, 1.7847 v, 25.6 r, 23.0172 11 0.2433 n, 1.5891 v, 6.10 r 2.0662 d, 1.0668 r, 30.4548 11, 0.1910 r 2.759s d, 0.0255 n, 1.67 v. 57.3 r, 3.0080 11,, 0.5681

7 n 1.6668 v, 33.0 r, -40.5882 d, 0.8687 r --10.6177 11 0.2433 n. 1.7865 v, 50.1 r 1.0641 d 0.8722

n, 1.6034 v, 38.0 r, 8.5301 d 1.2638 r 82.8l54 d 0.5340

n, 1.5184 1 60.1 r 3.l680 11,, 0.0243 r., 3.2395 11,, 0.1825

r1, 1.9225 11 20.9 r, 1.8270 d 0.7992

n 1.5184 v 60.1 r -2.8557

f ifiza f Back focus F 4.5616

single negative meniscus with its convex surfaces directed to the object side, the second lens component consisting of two lens elements cemented to each other to form a negative meniscus as a whole with the convex surfaces thereof directed to the object side, the third lens component consisting of two lens elements cemented to each other to form a negative lens as a whole, the fourth lens component consisting of two lens elements, a positive and a negative cemented to each other to form a positive lens as a whole, the fifth lens component consisting of a single positive meniscus with its concave surfaces directed to the object side, while the sixth lens component consists of two lens elements cemented to each other to form a positive lens as a whole, said photographic lens satisfying the following conditions:

f 1f12z1| f n n 15f r 35f 11 11 ;f r 3.5f

(3) f r 3.5f

(5) where:

f resultant focal length of the entire system f resultant focal length of the first, the second and the third lens components inclusive r, (i 1 16) the radius of curvature of each of the surfaces of the lens elements, 1 beginning at the object side d, (i= 1 15)= the thickness of each of the lens elements and the air gap between the adjacent lens elements, i beginning at the object side n, (i 1 10) the refractive index of each of the lens elements, i beginning at the object side 11,- (i 1 10) Abbe number of each of the lens elements, i beginning at the object side.

2. Ultra-wide angle photographic lens according to claim 1, which satisfies the following numerical data:

n, 1.5891 11, 61.0 r, 2.5106 d, 2.3830 r 8.4135 d; 0.5167

n, 1.5891 11, 61.0 r; 2.1550 11, 1.7556 r -37.9278 d 0.1945

n 1.67 v, 57.8 r, 2.1550 d 0.5957

n, 1.6668 v, 33.0 r, 12.2238 11 1.0057 r, 18.9741 d, 0.2432

n 1.7865 :1 50.1 r 1.3584 d 0.8377

n 1.6032 1 42.3 r 5.60l2 4,, 1.5210 n, -7.7271 d 0.5678

n, 1.5173 v, 69.3 r --3.1809 11,, 0.0243 r 3.3374 d 0.1824

f= 1.0 ;f =-1.545f

Back Focus f 4.5855

3. In an ultra-wide angle photographic lens consisting of six lens components, the improvement wherein the first lens component beginning at the object side is a single negative meniscus with its convex surfaces directed to the object side, the second lens component consisting of two lens elements, a positive and a negative cemented to each other to form a negative meniscus as a whole with the convex surfaces thereof directed to the object side, the third lens component consisting of two lens elements closely spaced from each other by a small air gap to provide a negative power as a whole, the fourth lens component consisting of two lens elements cemented to each other to form a positive lens as a whole, the fifth lens component consisting of a single positive meniscus with its concave surfaces directed to the object side, while the sixth lens component consists of two lens elements cemented to each other to form a positive lens as a whole, said photographic lens satisfying the following conditions:

f ff 2.5f

where:

f resultant focal length of the entire system f resultant focal length of the first, the second and the third lens components, inclusive r, (i 1 17) the radius of curvature of each of the surfaces of the lens elements, 1' beginning at the object side d, (i 1 16) the thickness of each of the lens elements and the air gap between the adjacent lens elements, 1' beginning at the object side n, (i 1 10) the refractive index of each of the lens elements, i beginning at the object side v, (i 1 10) Abbe number of each of the lens elements, 1' beginning at the object side 4. Ultra-wide angle photographic lens according to claim 3, which satisfies the following numerical data:

f 1.0;f z3 Back Focusf 4.5616 

1. In an ultra-wide angle photographic lens consisting of six lens components, the improvement wherein the first lens component beginning at the object side is a single negative meniscus with its convex surfaces directed to the object side, the second lens component consisting of two lens elements cemented to each other to form a negative meniscus as a whole with the convex surfaces thereof directed to the object side, the third lens component consisting of two lens elements cemented to each other to form a negative lens as a whole, the fourth lens component consisting of two lens elements, a positive and a negative cemented to each other to form a positive lens as a whole, the fifth lens component consisting of a single positive meniscus with its concave surfaces directed to the object side, while the siXth lens component consists of two lens elements cemented to each other to form a positive lens as a whole, said photographic lens satisfying the following conditions: f < f123 < 2.5f (1) n2> n3 ; 15f<r4 < 35f (2) Nu 4 > Nu 5 ; f< r7 < 3.5f (3) f <r15 < 3.5f (4) Nu 9 < 30 ; Nu 10 > 50 (5) where: f resultant focal length of the entire system f123 resultant focal length of the first, the second and the third lens components inclusive ri (i 1 - 16) the radius of curvature of each of the surfaces of the lens elements, i beginning at the object side di (i 1 - 15) the thickness of each of the lens elements and the air gap between the adjacent lens elements, i beginning at the object side ni (i 1 - 10) the refractive index of each of the lens elements, i beginning at the object side Nu i (i 1 - 10) Abbe number of each of the lens elements, i beginning at the object side.
 2. Ultra-wide angle photographic lens according to claim 1, which satisfies the following numerical data: r1 11.8788 d1 0.3404 n1 1.5891 Nu 1 61.0 r2 2.5106 d2 2.3830 r3 8.4135 d3 0.5167 n2 1.7847 Nu 2 25.6 r4 18.4891 d4 0.2432 n3 1.5891 Nu 3 61.0 r5 2.1550 d5 1.7556 r6 -37.9278 d6 0.1945 n4 1.67 Nu 4 57.8 r7 2.1550 d7 0.5957 n5 1.6668 Nu 5 33.0 r8 12.2238 d8 1.0057 r9 18.9741 d9 0.2432 n6 1.7865 Nu 6 50.1 r10 1.3584 d10 0.8377 n7 1.6032 Nu 7 42.3 r11 -5.6012 d11 1.5210 r12 -7.7271 d12 0.5678 n8 1.5173 Nu 8 69.3 r13 -3.1809 d13 0.0243 r14 3.3374 d14 0.1824 n9 1.9229 Nu 9 20.9 r15 2.0547 d15 0.6237 n10 1.5173 Nu 10 69.3 r16 -3.6401 f 1.0 ; f123 -1.545f Back Focus fB 4.5855 .
 3. In an ultra-wide angle photographic lens consisting of six lens components, the improvement wherein the first lens component beginning at the object side is a single negative meniscus with its convex surfaces directed to the object side, the second lens component consisting of two lens elements, a positive and a negative cemented to each other to form a negative meniscus as a whole with the convex surfaces thereof directed to the object side, the third lens component consisting of two lens elements closely spaced from each other by a small air gap to provide a negative power as a whole, the fourth lens component consisting of two lens elements cemented to each other to form a positive lens as a whole, the fifth lens component consisting of A single positive meniscus with its concave surfaces directed to the object side, while the sixth lens component consists of two lens elements cemented to each other to form a positive lens as a whole, said photographic lens satisfying the following conditions: f < f123 < 2.5f (1) n2> n3 ; 15f <r4 < 35f (2) Nu 4> Nu 5 ; f< r7 ; r8 < 3.5f (3) 3) f < r16 < 3.5f (4) 4) Nu 9 < 30 ; Nu 10 > 50 (5) where: f resultant focal length of the entire system f123 resultant focal length of the first, the second and the third lens components, inclusive ri (i 1 --- 17) the radius of curvature of each of the surfaces of the lens elements, i beginning at the object side di (i 1 - 16) the thickness of each of the lens elements and the air gap between the adjacent lens elements, i beginning at the object side ni (i 1 - 10) the refractive index of each of the lens elements, i beginning at the object side Nu i (i 1 - 10) Abbe number of each of the lens elements, i beginning at the object side
 4. Ultra-wide angle photographic lens according to claim 3, which satisfies the following numerical data: r1 12.5508 d1 0.3406 n1 1.5891 Nu 1 61.0 r2 2.3973 d2 2.0581 r3 6.7504 d3 0.4841 n2 1.7847 Nu 2 25.6 r4 23.0172 d4 0.2433 n3 1.5891 Nu 3 61.0 r5 2.0662 d5 1.0668 r6 -30.4548 d6 0.1910 n4 1.67 Nu 4 57.3 r7 2.7598 d7 0.0255 r8 3.0080 d8 0.5681 n5 1.6668 Nu 5 33.0 r9 -40.5882 d9 0.8687 r10 -10.6177 d10 0.2433 n6 1.7865 Nu 6 50.1 r11 1.0641 d11 0.8722 n7 1.6034 Nu 7 38.0 r12 -8.5301 d12 1.2638 r13 -82.8154 d13 0.5340 n8 1.5184 Nu 8 60.1 r14 -3.1680 d14 0.0243 r15 3.2395 d15 0.1825 n9 1.9229 Nu 9 20.9 r16 1.8270 d16 0.7992 n10 1.5184 Nu 10 60.1 r17 -2.8557 f 1.0 ; f 123 - 2.04f Back Focus fB 4.5616 . 